Expansible sealing elements are generally known and used to a wide extent for various purposes. It is also known to expand such sealing elements by means of a filling medium which is forced into a cavity in the element after which the filling medium can harden so that the expanded sealing shape of the sealing element is retained. Examples of elements intended to be filled with a medium which, at least on injection into the cavity, has the form of a liquid are disclosed inter alia in FR Pat. No. 835 966, FR Pat. No. 1 375 644, DE Pat. No. 1 475 890 and U.S. Pat. No. 2,760,791. In the U.S. Pat. No. 3,341,974 there is disclosed a sealing element with an encircling cavity which expands from one side of a partition round the sealing element to the opposite side of the partition. Inlets and outlets for a liquid are disposed in both end portions of the cavity, that is to say in the region adjacent to the two sides of the partition.
A limitation of the sealing elements of the general kind given above is that, in the present stage of development, they are not particularly suitable when the filling medium consists of a material with a comparatively long hardening time. This is actually a serious disadvantage because some of the filling media most suitable for other reasons consist precisely of materials with comparatively long hardening times. The reason why long hardening times constitute a problem is that the filling medium must retain excess pressure until the material has solidified completely. With forms of embodiments of sealing elements hitherto known, therefore, the pressure source cannot be uncoupled until the material has solidified, which makes handling complicated and/or involves a low productivity expressed in number of sealing elements finished per unit of time. Against this background, rapid hardening filling media have hitherto mainly been used despite the fact that these have certain definite disadvantages, inter alia from the environment point of view.